Method of increasing the resonance capacity of wood.



' R. MARKSTEIN.

METHOD OFINCREASING THE RESONANCE CAPACITY OF WOOD.

APPLICATION FILED JAN. 20. I9I3.

Patented Nov. 9, 1915.

ATTO EY SHINGTON. D. c

FTQE.

ROBERT MARKSTEIN, OF VIENNA, AUSTRIA-HUNGARY, ASSIGNOR OF ONE-HALF TO ARTHUR LION AND ROBERT LION, OF VIENNA, AUSTRIA-HUNGARY.

METHOD OF INCREASING THE RESONANCE CAPACITY OF WOOD.

Application filed January 20, 1913.

T0 aZZ whom it may concern Be it known that 1, ROBERT MARKSTEIN, subject of the Emperor of Austria-Hungary, residing at Czartoryskigasse 56, Vienna, Xi ITI, in the Province of Lower Austria and Empire of Austria-Hungary, have in vented certain new and useful Improvements in Methods of Increasing the Resonance Capacity of Wood, of which the following is a specification.

The invention relates to a method for increasing the resonance of wood.

It is an object of the invention to subject plates or strips of wood which are to be used as sound boards to a treatment which will increase the resonance capacity of the wood.

Another object of the invention is to continue this increase by deformation of the wood plates and to provide a treatment which will make this deformation permanent.

With these and other objects in view I have illustrated in the accompanying drawing diagrammatically portions of a plate of wood at different stages of the method.

In the drawing Figure 1 shows a pair of rollers with resilient covering and a section through a plate or board of wood part of which has been subjected to the rolling operation. Fig. 2 is a section through a board provided on certain portions with a coating to protect said portions against the actlon of certain chemicals, and Fig. 3 shows diagrammatically the section through the same board after having been subjected to the action of said chemicals.

In treating sound boards of string instruments with a view to increase their resonance, it has already been proposed to reduce the softer parts of the wood and to produce thereby a ribbed or wave surface either by the use of a sand blast acting on the softer portions only or by the application of a corrosive or abrading substance which attacks the soft parts in preference to the mature or hard parts of the wood. It has also been proposed to compress the softer parts which lie between the hard parts by means of a tool like a stencil in order to produce a ribbed surface. In

contra-distinction to these known methods the present invention relates to a method by which the resonance capacity of wood of any thickness of formation is increased by the Specification of Letters Patent.

Patented Nov. 9, 1915.

Serial No. 743,218.

wood being rolled between rubber thereby avoiding cracks or tearings in the material, as the rolling causes the so-called flux of the matter. But the internal or surface strain produced in the wood by the rolling pressure aided by atmospheric moisture and the vibrations would be able to flatten the waved surface produced by the rolling action. In order to obviate the said converting or flattening of surface one side will be planed after the rolling process and then moistened, or also both sides will be moistened. By the moistening on one side resistance of the wood cells is highly diminished. The internal or surface strain -will be larger in the hard portions of the wood than in the relatively plastic intermediate portions. If then the resistance or internal strain on the hard portions is diminished on one side by moistening the wood, these harder portions will be subject to the surface and internal strain on the hard portions on the opposite surface and will be drawn inwardly so that the wave lines defining the two surfaces of the board will become equidistant from each other. The slits in the harder portions give way to the pressure of the opposite side, said pres sure being accumulated as tension, and as a result an inverted corrugation will be formed on the moistened side, i. 6., the annual rings lie at a lower level on this side than the soft wood, contrary to the other side. In order to compensate cracks produced in the wood by a too hi h rolling pressure a suitable varnish is used.

Fig. 1 shows a section through a portion of a board, the section through the annular rings or hardened portions of the wood being indicated by narrower cross-sectioning than the softer parts. Owing to the different hardness of the wood portions the compression to which the wood is subjected by being drawn through an interspace between rollers 7 with resilient covering 8, the portions 2 of softer material will be compressed more than the portions of harder material. The board therefore will assume a sectional shape as indicated in Fig. 1. The more plastic soft material 2, owing to the nature of this material, is not subject to heavy internal strains, the hard material however is subject to the strains which are indicated by way of example by the arrows 3 in Fig. 1. If then one surface, as for instance the upper surface of the board is moistened this internal strain will have the effect of drawing the harder surface portions more inwardly or in direction toward the raised portion of the opposite surface, than the softer surface portions. The wave line shown on the upper surface in Fig. 1 will be inserted showing an amplitude directed downwardly, where previous to the moistening this amplitude extended upwardly. As the internal strain on the other surface is permanent the deformation to which the wood has been subjected by the rolling treat ment in combination with the moistening treatment will also be permanent even if the moisture should evaporate. As stated above between the two stages of the method one surface, in the present instance the upper surface, may be planed to enhance the desired effect. Moreover the soft wood may also be corroded or etched out by means of chemical substances for example chromic acid, after a matrix has been formed previously by a photographic chemical process, which matrix protects the annual rings against the influence of the chemical sub stances; or after the said annual rings have been protected by covering, coating or impregnating the same with paraiiin, wax or any substance, which is not affected or attached by the respective chemicals. This preliminary treatment ofthe wood for reducing the section of the softer parts chemically is illustrated by way of example in Figs. 2 and 3. According to Fig. 2 the board 4: which is shown in cross section is provided on the upper surface with a coating of paraflin or the like, shown diagrammatically at 5. The intermediate surface portions of the soft material 2 are subjected to a treatment of some etching acid indicated at 6. The effect of this chemical preliminary treatment on the wood will be the production of a wave surface similar to the upper surface shown in Fig. 1. The coating of parailin may then be removed and the wood may be subjected to the rolling operation as described above.

The present method may be adapted to all musical or other instruments with vibrating wood parts.

Claim:

1. A method of increasing the resonance.

capacity of wood which consists of subjecting the wood to a rolling operation between rollers provided with resilient covering and producing thereby a ribbed surface, the harder portions of the wood giving way to the rolling pressure to a less extent than the softer portions and planing and moistening the wood at least on one of said surfaces.

2. A method of increasing the resonance capacity of wood which consists of subjecting one surface of the wood to an etching chemical after the harder portions on said surface have been protected by a substance which is not attacked by said chemical, subjecting the woodtreated in this manner to a rolling operation between rollers whereby the harder portions of the wood not giving way to the pressure to the same extent as the softer portions, project beyond said softer portions and planing and moistening one surface of the wood.

In testimony whereof I have hereunto set my hand in presence of two subscribing witnesses.

ROBERT MARKSTEIN. Witnesses:

SIGMUND BAUER, AUGUST FUzznR.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, D. C. 

